(function(win, lib) {
  var doc = win.document;
  var docEl = doc.documentElement;
  var metaEl = doc.querySelector('meta[name="viewport"]');
  var flexibleEl = doc.querySelector('meta[name="flexible"]');
  var dpr = 0;
  var scale = 0;
  var tid;
  var flexible = lib.flexible || (lib.flexible = {});
  
  if (metaEl) {
  //console.warn('将根据已有的meta标签来设置缩放比例');
  var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/);
  if (match) {
  scale = parseFloat(match[1]);
  dpr = parseInt(1 / scale);
  }
  } else if (flexibleEl) {
  var content = flexibleEl.getAttribute('content');
  if (content) {
  var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
  var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
  if (initialDpr) {
  dpr = parseFloat(initialDpr[1]);
  scale = parseFloat((1 / dpr).toFixed(2));
  }
  if (maximumDpr) {
  dpr = parseFloat(maximumDpr[1]);
  scale = parseFloat((1 / dpr).toFixed(2));
  }
  }
  }
  
  if (!dpr && !scale) {
  var isAndroid = win.navigator.appVersion.match(/android/gi);
  var isIPhone = win.navigator.appVersion.match(/iphone/gi);
  var devicePixelRatio = win.devicePixelRatio;
  if (isIPhone) {
  // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
  if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
  dpr = 3;
  } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
  dpr = 2;
  } else {
  dpr = 1;
  }
  } else {
  // 其他设备下，仍旧使用1倍的方案
  dpr = 1;
  }
  scale = 1 / dpr;
  }
  
  docEl.setAttribute('data-dpr', dpr);
  if (!metaEl) {
  metaEl = doc.createElement('meta');
  metaEl.setAttribute('name', 'viewport');
  metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
  if (docEl.firstElementChild) {
  docEl.firstElementChild.appendChild(metaEl);
  } else {
  var wrap = doc.createElement('div');
  wrap.appendChild(metaEl);
  doc.write(wrap.innerHTML);
  }
  }
  
  function refreshRem(){
  var width = docEl.getBoundingClientRect().width;
  if (width / dpr > 540) {
  width = 540 * dpr;
  }
  var rem = width / 10;
  docEl.style.fontSize = rem + 'px';
  flexible.rem = win.rem = rem;
  }
  
  win.addEventListener('resize', function() {
  clearTimeout(tid);
  tid = setTimeout(refreshRem, 300);
  }, false);
  win.addEventListener('pageshow', function(e) {
  if (e.persisted) {
  clearTimeout(tid);
  tid = setTimeout(refreshRem, 300);
  }
  }, false);
  
  if (doc.readyState === 'complete') {
  doc.body.style.fontSize = 12 * dpr + 'px';
  } else {
  doc.addEventListener('DOMContentLoaded', function(e) {
  doc.body.style.fontSize = 12 * dpr + 'px';
  }, false);
  }
  
  
  refreshRem();
  
  flexible.dpr = win.dpr = dpr;
  flexible.refreshRem = refreshRem;
  flexible.rem2px = function(d) {
  var val = parseFloat(d) * this.rem;
  if (typeof d === 'string' && d.match(/rem$/)) {
  val += 'px';
  }
  return val;
  }
  flexible.px2rem = function(d) {
  var val = parseFloat(d) / this.rem;
  if (typeof d === 'string' && d.match(/px$/)) {
  val += 'rem';
  }
  return val;
  }
  
  })(window, window['lib'] || (window['lib'] = {}));